Blade control system with reactive pickup



NKWR 17, 1964 D. E. ATKINSON 3,156,989

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AT TORN EYS j/Zw United Sates Patent 3,156,989 BLADE CONTROL SYSTEM WITH REACTIVE PICKUP Duane E. Atkinson, 102 Fey Drive, Burlingame, Calif. Filed Nov. 30, 1960, Ser. No. 72,645 4 Claims. (Cl. 37-143) This invention relates generally to vehicle control sysstems and more particularly to such systems which are guided by a reactive pickup.

In leveling a road bed in preparation for paving, it is necessary that the grading be even and accurate. It is well known that specifications for the paving of road beds is determined from several factors, among which is the finished elevation of the paved road and the thickness of the paving. Consequently, the road bed must be below the desired finished road surface at least a distance equal to the specified thickness of the paving.

. In addition, it is realized that in the actual construction of the paved road, large amounts of material are employed. If the final road bed has been prepared deeper than is required by the specification, the additional thickness of the paving material to bring the road elevation up to the required elevation creates a large additional expense on the contractor.

By present methods, the road bed is roughly graded by bulldozers or other such equipment to a preliminary level. Subsequently, a line is stretched and suspended along the road bed by surveyors, The line not only indicates the general horizontal location of the road but indicates, in addition the actual level of the desired road surface. Using the line as a guide, the road bed is again graded keeping a predetermined distance below the line which is stretched. This operation may include digging a trench along the line with subsequent laying of rails or it may include overall grading of the entire road surface. When the rail trench alone is dug, the rails are laid and serve as a guide for leveling the remainder of the road surface.

At present, this finished leveling either of therail trench or of the entire bed is accomplished by the operator of the final grading apparatus observing the line and visually keeping the proper position of the cutting blade.

More recently advances-have been made in the art wherein road leveling may be accomplished in an automatic or semi-automatic operation. In some of these operations, levers are disposed about the stretched line and serve to contact the line and mechanically activate a switch for adjusting the blade. Although such a system is definitely an advance in the art of road leveling, it has several disadvantages. The flexing of the stretched line is inherent in applying force to throw the switch as is the actual movement of the arm in order to activate the switch. Each of these deficiencies causes an error in the position of the blade.

Such errors, although small in themselves, create considerable expense on the contractor due to the large amount of materials involved in laying the paved road. Other automatic and semi-automatic systems which have been devised include pendulums, gyroscopes, depth pressure gauges, visual level indications, and mercury switches. Each of these has had little success due to their fragile nature, expense or reliance on human judgment.

Moreover, in the leveling of other surfaces such as beds for pipelines and drainage ditches, an accurate finished surface is desirable.

It is, therefore, an object of this invention to provide an improved vehicle control system.

It is a more particular object of this invention to provide an improved vehicle control system wherein a stretched electrically conductive line, indicative of the finished surface, is utilized as a conductor; and sensing means disposed on grading equipment and about the line serve as a sensing reactive pickup from the line for guiding the grading blade.

It is another object of this invention to provide a vehicle control system of the aforementioned character wherein the sensing means serves to adjust the blade.

These and other objects of the invention will become more clearly apparent upon reading the following description in conjunction with the accompanying drawing.

Referring to the drawing:

FIGURE 1 is a perspective view of a grading vehicle in operation in accordance with the present invention;

FIGURE 2 is an enlarged view of a portion of FIGURE 1 showing the novel pickup apparatus in accordance with the invention;

FIGURE 3 is an enlarged view showing a reactive pickup device using an inductive reactance in accordance with the invention;

FIGURE 4 is an enlarged view showing a reactive pickup device employing a capacitive reactance in accordance with the invention;

FIGURE 5 is a schematic block diagram of an electrical circuit as used in accordance with one embodiment of the invention utilizing an inductive pickup;

FIGURE 6 is a schematic diagram of one phase detector as used with inductive reactance in accordance with the invention; and

FIGURE 7 is a schematic diagram of an electrical circuit as used in accordance with another embodiment of the invention utilizing a capacitive pickup;

FIGURE 8 is a schematic diagram of an electrical circuit as used in accordance with still another embodiment of the invention utilizing a capacitive pickup; and

FIGURE 9 is a schematic diagram showing one way of subtracting rather than adding the outputs of the phase detectors shown in FIGURE 5.

Referring to FIGURE 1, an electrically conductive line 11 is shown stretched between the posts 13. The line 11 is grounded at each end thereby forming a closed loop with ground. A grading tractor 19 is shown in operation adjacent to the line 11 in the road bed 21. The tractor includes a cutting blade 23 and a final leveling blade 25, which are in fixed relationship with each other to operate at the same level. A pickup 27 is disposed about the line 11. The pickup is aflixed to but insulated from the blade and serves to provide a reactive signal for blade adjustment in a manner to be described hereinafter.

The tractor 19 also includes an electromagnetic wave radiator 28 disposed adjacent the line 11 but separated from the pickup 27. The radiator serves to induce a current in the loop including the line 11 and ground.

Since the system operates on a reactive pickup principle, it is unnecessary to contact the line 11. Consequently, there is no deflection of the line and there is relatively little play or error in the system.

Referring to FIGURES 2, 3 and 4, it is seen that the pickup 27 is generally disc-shaped with a slot extending upwardly from the bottom thereof and terminating above the center. The pickup is disposed on the blade 25 having its axis parallel to the direction of motion of the vehicle and line 11 itself. The pickup includes a disc 31 made of plastic or other suitable material. Reactive elements embedded therein are disposed at intervals at 45 from the horizontal. The spacing of the reactive elements and the slot 33 are such as to permit the passage of the post 13 therethrough such that the line 11 may occupy that area in the center of the disc 31.

Referring more particularly to FIGURE 3, the reactive elements shown are inductors 35-38. It is seen that the diametrically opposed inductors 35 and 37 are serially connected and have terminals 41 and 43. Likewise, the diametrically opposed conductors 36 and 38 are serially connected and have the terminals 45 and 47. An addi may be utilized as a reference signal.

tional terminal 49 connected to the center of the opposed inductors 36 and 38 is employed to secure a reference phase as will be described hereinafter.

The capacitive reactor pickup, as shown in FIGURE 4, likewise employs four reactances disposed 90 apart and 45 from the horizontal. The reactance pickups in this case include the capacitance plates 51-54,

In the embodiments of the pickups shown in FIGURES 3 and 4, the slots 33 are disposed in the bottom of the base 31. It is apparent that if the posts 13 are arranged other than vertical, the opening 33 should be disposed in such a manner as to receive the posts. Moreover, the slot 33 may be disposed in a horizontal plane whereby the line 11 enters the pickup through the side. With such an arrangement, the pickup devices may be secured at right angles to a spring urged pivoted device. Such a device is described and claimed in applicants copending application entitled Vehicle Control System With Electrical Contact, filed June 20, 1960, Serial No. 37,369, now Patent No. 3,044,195. It is also apparent that the pickup may include elements supported by a toroid or other means.

, FIGURE 5 shows a block schematic diagram of one embodiment of the invention utilizing an inductive reactance pickup. As seen, the output of the serially connected coils 36 and 38 is applied through the terminal 47 and amplifier 56 to a phase detector 57. Likewise, the outputs of the series inductors 35 and 37 are applied through an amplifier 58 to a phase detector 59. The phase reference signal appearing across the inductor 36 is applied through the terminal 49 and amplifier 50 to both the phase detectors 57 and 59. The output of the phase detector 57 is applied through the terminals 60a and 60b across the resistor 61, while the output of the phase detector 59 is applied through the terminals 62a and 62b across the resistor 63. The resistors 61 and 63 are serially connected and the extremities of the series connection are connected to the output terminals 65 and 67. A source of alternating current voltage 69 is coupled to the line 11 by the reactance 71. The signal source '69 may be coupled to the line 111 by reactive coupling means located on the vehicle in proximity to the line but spaced from the pickup device 27 as schematically illustrated in FIGURE 1.

- In operation, the high frequency current flows in the loop including the line 11 and ground. This current creates electromagnetic fields which are coupled to the inductors 35-38. The inductors 36 and 38 are wound so as to receive the signal from the line 11 in opposite phase. The inductors 35 and 37 are likewise wound to receive signals of opposite phase. If the line 11 is disposed closer to the inductor 36, a greater voltage will be induced in that inductor than in the inductor 38. Consequently, the overall voltage induced in the series combination including the inductors 36 and 38 will have a phase representative of that in the inductor 36, keeping in mind that the phase differences between the inductors 36 and 38 are 180.

The phase reference signal may be derived in any man ner which is indicative of the phase applied. Thus, the signal appearing across one of the inductors such as 36 Alternatively, the reference signal may be derived directly from the signal supply 69 if a phase adjustor circuit is utilized, as will be described in conjunction with a capacitance circuit hereinafter with respect to FIGURE 7.

Thus, it is seen that if the predominant phase of the series inductors 36 to 38 is similar to the phase of the reference signal, the voltage output of the phase detector 57 will be of one polarity and will appear across the resistors 61. Conversely, if the overall phase characteristic of the series inductor combination is opposite to that of the reference source, the voltage output will be of the opposite polarity and will appear across the resistor 61.

The inductors 35-38 may be wound such that proximity of the line 11 to the inductors 35 and 38 causes an output of one sense from both of the phase detectors 57 and 59. Also, proximity of the line 11 to the inductors 36 and 37 causes an output of the opposite sense from both of the phase detectors 57 and 59.

Referring simultaneously to FIGURES 3 and 5, if the line 11 is located above its center position as shown in FIGURE 3, a greater voltage will be induced in the inductors 35 and 38. The reference signal in the example shown is taken from the inductor 36. The voltage phase output under these conditions will be represented across the resistor 61 by a positive DC. voltage Likewise the predominant voltage of the series combination including the inductors 35 and 37 will be that of the inductor 35. This signal is applied to the phase detector 59 along with the reference voltage to apply a positive DC. voltage across the resistor 63.

The series combination of resistors 61 and 63 serve to add the outputs of the phase detectors 57 and 59 thereby giving an overall voltage across the terminal 65 and 67 of plus-plus This overall voltage may be applied to a servo or solenoid unit which activates the blades locating mechanism to raise the blade thereby raising the pickup device 27. This action is repeated until the line 11 is centrally located.

It is obvious that if the line 11 is located below the center, the outputs of each of the phase detectors will be a negative D.-C. voltage. The total of the D.-C. voltages across the resistors 61 and 63, then, will be minus-minus and may serve to lower the blade.

If the line 11 is located in any position along the horizontal center of the pickup 27 the sum of the phase detector outputs will be zero. This can be seen by realizing that the inductors 35 and 36 are wound to produce opposite outputs from the phase detectors 57 and 59 when the line 11 bears, the same relation to each of them.

If rather than adding the outputs of the phase detectors 57 and 59, these are subtracted, a different orientation is accomplished. Thus, again referring to FIGURES 3 and 5, if the line 11 were located to the right of center as shown in FIGURE 3, a greater voltage will be induced in the inductors 35 and 36. Here again, since the inductor 35 has a greater portion of induced voltage, the voltage at the resistor 63 will be plus However, the output of the phase comparator 57 will be the opposite of that in the previous example and the voltage on the resistor 61 would ordinarily be minus thus making the sum voltage zero. To subtract, a phase inverter may be inserted between the output of one of the phase detectors, for example, the detector 57 as shown in FIG. 9. The voltage across the resistor 61 will be reversed and will also be plus Consequently, here again, the overall output across the terminal 65 and 67 wil be plusplus It is seen, therefore, that the subtraction circuit may be utilized to steer the vehicle in a horizontal direction while the addition process may be utilized to adjust the blade in a vertical direction.

Subtraction may also be accomplished by reversing one of the pairs of output terminals 60a and b or 6211 and b.

It is obvious that a converse arrangement may be utilized whereby the addition process is utilized to steer the vehicle while the subtractive process is utilized to adjust the blade. This variation may be accomplished merely by changing the direction of the windings in one of the series combinations of inductors.

FIGURE 6 is a schematic diagram showing the operation of the phase detector 57. It will be understood that the phase detector 59 operates in a similar manner. As is seen, the overall output of the series inductors 36 and 38 is connected across the primary 73 of the transformer 75. The reference signal from the terminal 49 is applied to the center tap of the secondary 77 of the transformer 75. One side of the secondary 77 is coupled to ground through the diode 79.and the parallel combination of the resistor 81 and capacitor 83. The other side of the secondary 77 is coupled to ground through the diode 85 and the parallel combination of the resistor 87 and capacitor 89. The output terminals 60a and 60b are connected to the junctions of the diodes 79 and 85 with their respective resistors 81 and 87.

In operation if the line 11 is disposed equidistant between the inductors 36 and 38, the voltage induced by the series combination of the inductors is self-cancelling and zero voltage appears at the primary winding 73. The reference voltage being applied to the center tap of the secondary 77 induces equal current through the diodes 79 and 85. Consequently there is no voltage differential between the opposite sides of the secondary 77 or across the output terminals 60a and 60b.

If however the line is disposed closer to one of the indoctors 36 or 38, a predominant voltage of one phase will be induced across the transformer 75. If for instance, the line is closer to the inductor 36, the induced voltage across the transformer 75 will, in the lower portion of the secondary 77, be aiding the reference voltage applied at the center tap thereby causing more conduction to the diode 79. At the same time the induced voltage will be bucking the reference voltage at the center tap 77 in the upper portion of the secondary 77 thereby producing less current through the diode 85. Consequently a voltage drop appears across the terminals 60a and 60b which is representative of the relative position of the line 11 in the pickup device 27.

Referring to FIGURE 7, a schematic diagram of the reactive pickup utilizing capacitive reactance is shown.

' Each of the capacitive plates 51 through 54 coact with the line 11 to form capacitors. The diametrically opposed plates 51 and 53 in conjunction with the line 11 form a pair of series capacitors which with the capacitors 91 and 93 form the legs of one bridge circuit 94. Diametric plates 52 and 54 and the capacitors 95 and 97 form the legs of a second bridge circuit 96. A source 69 is capacitively coupled to the line 11.

The output of the bridge circuit 94 is applied to the phase detector 98. A signal of reference phase is applied to the phase detector from the source 69 through a phase adjustor 99. The phase adjustor is provided whereby the phase relationships can be adjusted so that for correct positioning of the pickup, zero output is obtained. Similarly, the output of the bridge circuit 96 is applied to a phase detector 100 which has a signal of reference phase applied thereto.

In operation, when the line 11 is centrally disposed within the pickup device, the bridges 94 and 96 are balanced. No input is applied to the base detectors 98 and 100. If the line is disposed off center, the relative voltage induced in the capacitors 5154 will change and the phase of the input voltage to the detectors 98 and 100 will change correspondingly. The phase detectors then provide an output voltage to the load resistors 61 and 63. Operation is similar to that discussed with respect to the inductive circuit of FIGURE 1 and will not be described infurther detail.

FIGURE 8 shows another embodiment of the invention using capacitive reactances in the pickup device 27. As in FIGURE 7, the plates 51 and 53 coact with the capacitors 91 and 93 to form a bridge circuit 94. Similarly, the plates 52 and 54 coact with the capacitors 95 and 97 to form the bridge circuit 96. In this instance it is noted that the line 11 is merely grounded and that no signal is applied thereto. The reference signal source 69 is applied to the bridge circuits 94 and 96 through the terminals 101 and 103 on the one side and grounded to the line 11 on the other.

The output of the bridge circuit 94 is applied to the phase detector 105, while the output of the bridge circuit 96 is applied to the phase detector 107. The phase reference source 69 is also coupled to each of the phase detectors 105 and 107. In this particular embodiment, it is noted that the reference source applied to the phase detec- 6 tors and 107 is taken from the same side of the source 69 as applied to the terminals 101 and 103. The outputs of the phase detectors are applied across the resistors 61 and 63, respectively.

In operation, when the line 11 is centrally disposed within the pickup device 27, the bridges 94 and 96 are balanced. Consequently, no input is applied to the detectors 105 and 107 from the bridges. However, if the line is disposed closer to the plates 51 and 54, for instance, than it is to the plates 52 and 53, the bridges will become unbalanced. The proximity to the plate 51 increases the capacitance thereof thereby decreasing the impedance associated with the plate 51 and the line 11. Conversely, the impedance associated with the plate 53 increases. Consequently, an output current from the bridge 94 is out of phase or in phase with the applied signal voltage. Since, in this case, the plate 53 exhibits the greater impedance and since the reference voltage 69 is applied to the phase detector 105 from the same side of the reference source, the input current to the phase detector from the plate 53 and the capacitor 93 will lead the input from the reference source by 180. It is apparent that, if the reference input were taken from the opposite side of the source 69, the input current from the plate 51 and the capacitor 91 would be 180 in phase with the applied reference source.

On the other hand, if the line 11 is disposed nearer to the plates 52 and 53, the phase of the input current to the detector is reversed. It is seen, therefore, that in the embodiment shown in FIGURE 8 when the line 11 is disposed closer to one of the plates in a particular bridge circuit than to the other, the current applied to the associated detector has a phase angle in quadrature with the reference signal. If the other plate is closer to the line 11, the phase input from the same bridge circuit to the detector is still in quadrature but in the opposite sense. Consequently, the phase detectors determine whether the input from the bridges is leading or lagging the phase reference source 69 by 90 and also develops an output determined thereby. The output is applied across the resistors 61 and 63 in the same manner as related in the earlier embodiments.

Variations similar to those described in connection with FIGURE 5 may be utilized with the capacitive reactance. The circuit may be used not only to adjust the blade but also to steer the vehicle. As the circuit is shown in FIG URE 7, blade adjustment is accomplished by adding the voltage across resistors 61 and 63. Steering would be accomplished by subtracting these voltages. The converse could be accomplished by reversing the bridge connections at one diametrically opposed pair of the capacitive plates.

I claim:

1. In a vehicle control system, a vehicle having an adjustable blade, means for moving said blade responsive to an electrical signal, a lead line disposed above a surface to be leveled at a preselected elevation above the desired level surface, said line being electrically conductive, series connected reactance means aflixed to said blade, a source of reference frequency, means for coupling said source of frequency to said reactance means, said reactance means being disposed on diametrically opposite sides of said conductive line whereby variation in the location of said line between said reactance means will cause a variation in the current phase within the reactance means, means for comparing the current phase within said reactance means with the reference frequency, said last named means producing an output signal representative of said comparison, and means responsive to said output signal for adjusting said blade.

2. In a vehicle control system, a vehicle having an adjustable blade, means for moving said blade responsive to an electrical signal, a lead line disposed above a sur face to be leveled at a preselected elevation above the desired level surface, said line being electrically conductive, means for inducing an alternating current signal in said line, series connected reactance means atfixed to 7 8 1 blade and disposed on diametrically opposite sides of References Cited in the file of this patent said line means for comparing the phase of said induc ed UNITED STATES PATENTS alternating current signal with the signal on said series reactance means, said last named means producing an out- 2317'400 27, 1943 put signal representative of said comparison, and means 5 2,403,956 Schlesmger July 16, 1946 to adjust said blade responsive to said voutput signal. 2,604,512 Bacon y 1952 3. A vehicle control system as defined in claim 2 where- 2,742,099 Hagen p 17, 1956 in said reactive means are inductive reactances. 2,842,039 Swingle July 8, 1958 4. A vehicle control system as defined in claim 2 where- 2,892,152 Buisson June 23, 1959 in said reactive means are capacitive reactances. 10 2,898,550 Fischer Aug. 4, 1959 

1. IN A VEHICLE CONTROL SYSTEM, A VEHICLE HAVING AN ADJUSTABLE BLADE, MEANS FOR MOVING SAID BLADE RESPONSIVE TO AN ELECTRICAL SIGNAL, A LEAD LINE DISPOSED ABOVE A SURFACE TO BE LEVELED AT A PRESELECTED ELEVATION ABOVE THE DESIRED LEVEL SURFACE, SAID LINE BEING ELECTRICALLY CONDUCTIVE, SERIES CONNECTED REACTANCE MEANS AFFIXED TO SAID BLADE, A SOURCE OF REFERENCE FREQUENCY, MEANS FOR COUPLING SAID SOURCE OF FREQUENCY TO SAID REACTANCE MEANS, SAID REACTANCE MEANS BEING DISPOSED ON DIAMETRICALLY OPPOSITE SIDES OF SAID CONDUCTIVE LINE WHEREBY VARIATION IN THE LOCATION OF SAID LINE BETWEEN SAID REACTANCE MEANS WILL CAUSE A VARIATION IN THE CURRENT PHASE WITHIN THE REACTANCE MEANS, MEANS FOR COMPARING THE CURRENT PHASE WITHIN SAID REACTANCE MEANS WITH THE REFERENCE FREQUENCY, SAID LAST NAMED MEANS PRODUCING AN OUTPUT SIGNAL REPRESENTATIVE OF SAID COMPARISON, AND MEANS RESPONSIVE TO SAID OUTPUT SIGNAL FOR ADJUSTING SAID BLADE. 